In oil and gas wells, metal seals are sometimes used to seal between structures in well tools, and in equipment used in other environments. However, several problems are frequently encountered when metal seals are used. For example, metal seals require very smooth and clean surfaces to seal against, and most metals can only be elastically deformed to a limited extent (which thereby limits the biasing force available from elastically deforming a metal seal), etc.
Elastomeric and other types of nonmetal seals may provide the ability to seal against irregular and unclean surfaces, and may provide sufficient resilient biasing force for urging the seals against the surfaces. However, nonmetal seals tend to degrade rapidly when used in dynamic configurations, i.e., where the seal must contact a moving surface while sealing against a pressure differential, or where the seal loses contact with the surface while the pressure differential still exists across the seal.
Metal to metal seals are preferred in some applications over elastomeric seals. An advantage of metal to metal seals is their wear capabilities, a property that is needed for dynamic seals and especially important when unloading pressure (when a seal opens up with a pressure differential such as in valves). Radial metal to metal seals that have two points of contact that will only seal in one direction like, for example, metal C-ring seals. To seal in both directions one needs at least four points of contact. The problem with having four points of contact is that they create pressure traps between them that can significantly increase stroking pressure.
Therefore, a need has arisen for an improved metal to metal seal for reliable low and high pressure sealing.